1. Field of the Invention
The present invention relates generally to magnetic read heads, and more specifically to stabilizing magneto-resistive sensors.
2. Background of the Invention
There are several ways to fabricate magneto-resistive (MR) sensors for read back of data on magnetic tape. A bias method is used in order to permit the sensor to operate in the linear portion of the MR curve. In some cases, two elements can be used at the same time, reading the same data, to reduce signal distortion. This is accomplished by processing the signal differentially so that any nonlinearities arising from the shape of the MR curve are canceled out.
In a coupled element design, the two elements may be placed atop each other in close proximity. This allows the sensors to provide magnetic bias for each other, as well as providing the benefits of differential sensing. The design has an added benefit of high output, since two elements occupy the same space that one element would occupy under normal circumstances.
One of the difficulties in making coupled element sensors is that for high linear densities, gap lengths must be made very small. Therefore, the films that make up the MR sensors are separated by a very thin insulator. Furthermore, because of the stacked nature of the design, all interconnection metallization must traverse steps where one material ends, and insulating material tends to become thinner.
The use of cobalt zirconium tantalum (CZT) shields on aluminum-titanium-carbide (AlTiC), instead of ferrite, creates problems with magnetic domain asymmetry and stability. The magnetic domains are unstable and have a tendency to form domain walls in inappropriate geometries. In other words the location of domain walls of the magnetic structure is not constant or repeatable.
There is always at least one magnetic domain associated with a magnetic structure. The key to stability is to make sure that the location of the domain wall does not move around and is predictable. Some types of read heads have active stabilization of magnetic domains, using permanent magnets, exchange coupling, and/or gratings. However, dual stripe read head designs do not have active stabilization. It is extremely difficult to use active stabilization on dual stripe heads and is not considered “manufacturable” within the industry. Currently, dual stripe heads do not have any intentional passive stabilization built into them.
Therefore, it would be desirable to have a method for passively stabilizing magnetic domains for dual stripe MR multi-track tape heads.